Your voltage regulator should allow 7.3 volts at high idle with no accessories turned on. If you're only seeing 5 volts, then chances are it isn't working. Check all connections to be sure none are corroded. If the cover on the regulator can be removed, you can also dress the contacts...sometimes they corrode or get sticky. Do this with the battery disconnected.
A fuel tank recently appeared on ebay, good trunk hinges are harder to find. If you're a club member, place a want ad in the bulletin.